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ONLINE COVER With the help of citizen scientists, researchers have discovered two radio-quiet gamma ray millisecond pulsars (MSPs), or spinning neutron stars, one of which is the only known MSP to remain undetected in radio observations. Since many gamma-ray MSPs are not detectable from Earth, the method used in this study may help future efforts related to determining the true population of MSPs. MSPs spin hundreds of times per second and seem to pulsate as their emission beams cross the Earth's line of sight. The Large Area Telescope (LAT), which launched on the Fermi Gamma-ray Space Telescope in 2008, has discovered more than 200 gamma-ray pulsars, half of which are MSPs and the other half of which originate from unknown sources. However, pulsations from gamma-ray pulsars can only be found by "blindly" searching through Fermi's data for pulsations at unknown frequencies. With the help of Einstein@Home, a
volunteer computing system, Colin J. Clark, his colleagues and the public searched through 5.5 years' worth of Fermi data for pulsations from unidentified sources. Their efforts resulted in detecting 17 young pulsars, including two radio-quiet gamma-ray MSP pulsars, each at different frequencies. CREDIT: DANA BERRY/SKYWORKS/NASA